I would say two things: First, STCKF is potentially so much faster than STCK that it is probably well worth it even if you have to test a flag and branch.
Second, I am going to guess that you are safe assuming STCKF is here to stay. In my 55 years on this platform I have seen very, very few non-privileged hardware instructions go away. TBEGIN and friends was a shocking exception and I doubt very much that it will become the rule. TBEGIN was probably problematic from the get-go and should not have been introduced; not so STCKF which is fundamentally just a dumbed-down STCK. Also, don't forget about the option of STCKE. Charles -----Original Message----- From: IBM Mainframe Assembler List <ASSEMBLER-LIST@LISTSERV.UGA.EDU> On Behalf Of Mario Bezzi Sent: Thursday, April 10, 2025 11:51 PM To: ASSEMBLER-LIST@LISTSERV.UGA.EDU Subject: Store-Clock-Fast Facility PoP states "The store-clock-fast facility *may* be available on a model implementing z/Architecture." The "may" word forces my performance sensitive code to go through additional controls before using STCKF, which sort of defeats the purpose of the instruction. STCKF was first introduced in 2005 and has been available in any CPC generation since then. If I could rely on it being always available I would have less code to run and maintain. Is there documentation stating which facilities are available in a given CPC family? What others do? PoP states the same for Transactional-Execution Facility, still IBM started warning long in advance about its withdrawal. Thank you! mario
